研究者詳細 - 角皆　潤

論文 - 角皆　潤

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Contribution of methane to total gas pressure in deep waters at lakes Nyos and Monoun (Cameroon, West Africa) 査読有り

Issa, T. Ohba, F. Wilson, Y. Yoshida, F. Alain, M. Kusakabe, U. Tsunogai, Y. Oginuma, C. T. Boris, G. Tanyileke, S. Nkamdjou, H. Satake J.V. Hell

Geochemical Journal 47 巻 ( 3 ) 頁： 349-362 2013年

Coseimic massive methane release from a submarine mud volcano 査読有り

Tsunogai, U., K. Maegawa, S. Sato, D.D. Komatsu, F. Nakagawa, T. Toki, and J. Ashi

Earth and Planetary Science Letters 341-344 巻頁： 79-85 2012年8月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

We report here the discovery of two methane-enriched plumes in a water column above the Kumano Knoll 5 submarine mud volcano (KK-5) in Nankai Trough during 2004; a slight methane enrichment was observed in this region in 2000 and 2010. The deeper of the two plumes spread horizontally at depths near the top of KK-5, whereas a shallow plume spread at a height of 300 m from the top of KK-5. The end-member d¹³C values of methane in both plumes, -46.1+-4.8 per mil and -51.4+-5.8 per mil in the deep and shallow plumes, respectively, and methane extracted from sediment in KK#5 (-52+-2 per mil) are statistically indistinguishable. We conclude that the plumes were created by massive release of methane from KK#5 and that this event probably occurred in response to the large earthquakes (Mw 7.5) that occurred shortly before our observation in 2004. The discharge rates from submarine mud volcanoes (SMVs) in subduction zones may be highly variable in response to major earthquakes.

DOI： 10.1016/j.epsl.2012.06.004

Biogeochemical processes involving acetate in sub-seafloor sediments from the Bering Sea shelf break 査読有り

Ijiri, A., N. Harada, A. Hirota, U. Tsunogai, N.O. Ogawa, T. Itaki, B.-K. Khim, M. Uchida

Organic Geochemistry 48 巻頁： 47-55 2012年7月

Iron-based microbial ecosystem on and below the seafloor: a case study of hydrothermal fields of the Southern Mariana Trough 査読有り

Kato, S., K. Nakamura, T. Toki, J. Ishibashi, U. Tsunogai, A. Hirota, M. Ohkuma, A. Yamagishi

Frontiers in Microbiology 3 巻 2012年3月

Disturbance of deep-sea environments induced by the M9.0 Tohoku Earthquake 査読有り

Kawagucci, S., Y.T. Yoshida, T. Noguchi, M.C. Honda, H. Uchida, H. Ishibashi, F. Nakagawa, U. Tsunogai, K. Okamura, Y. Takaki, T. Nunoura, J. Miyazaki, W. Lin, H. Kitazato, and K. Takai

Scientific Reports 2 巻 2012年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

The impacts of the M9.0 Tohoku Earthquake on deep-sea environment were investigated 36 and 98 days after the event. The light transmission anomaly in the deep-sea water after 36 days became atypically greater (similar to 35 %) and more extensive (thickness similar to 1500 m) near the trench axis owing to the turbulent diffusion of fresh seafloor sediment, coordinated with potential seafloor displacement. In addition to the chemical influx associated with sediment diffusion, an influx of C-13-enriched methane from the deep sub-seafloor reservoirs was estimated. This isotopically unusual methane influx was possibly triggered by the earthquake and its aftershocks that subsequently induced changes in the sub-seafloor hydrogeologic structures. The whole prokaryotic biomass and the development of specific phylotypes in the deep-sea microbial communities could rise and fall at 36 and 98 days, respectively, after the event. We may capture the snap shots of post-earthquake disturbance in deep-sea chemistry and microbial community responses.

DOI： 10.1038/srep00270

First measurements of methane and its carbon isotope ratio in the Japan Sea (East Sea) 査読有り

Gamo, T., U. Tsunogai, A. Hirota, N. Nakayama, D.-J. Kang, K.-R. Kim

MARINE CHEMISTRY 128 巻頁： 92-99 2012年1月

記述言語：英語掲載種別：研究論文（学術雑誌）

We measured dissolved methane (CH₄) and its carbon isotope ratio (C-13/C-12 or delta C-13) from surface to bottom seawaters (maximum depth: 3574 m) for the first time in three major offshore areas of the Japan Sea (East Sea): the eastern Japan Basin, Yamato Basin, and Ulleung Basin. Seawater samples were taken during the KT-07-24 cruise of the R/V Tansei Maru in 2007 as part of a Japan-Korea collaborative study. The CH₄ concentration and its delta C-13(PDB) were obtained by continuous flow isotope ratio mass spectrometry. While the CH₄ concentrations of surface seawater were 2.6-3.8 nmol kg(-1), which was 43( +/- 22) % supersaturated compared to the atmospheric equilibrium values, those in the subsurface (D=30-150 m) showed much higher values up to 9.7 nmol kg(-1) (similar to 300 % supersaturation). This subsurface CH₄ had the minimum delta C-13 value of -54.3 parts per thousand (less than the atmospheric CH₄ value of -47 parts per thousand), implying a contribution from in situ microbial CH₄ production in some anoxic microenvironments. The CH₄ concentration decreased with depth toward minimum values of similar to 1 nmol kg(-1) (delta C-13, -30 to -40 parts per thousand.) at 1500-2000 m depth. Below a depth of 2000 m, we found a clear difference in CH₄ profiles among the three basins; in the eastern Japan Basin the CH₄ concentration remained almost constant down to the seafloor, while it gradually increased with depth up to > 2.0 nmol kg(-1) in the Yamato and Ulleung basins. This CH₄ increase toward the bottom was accompanied by a decrease of delta C-13-CH₄ to less than -50 parts per thousand, suggesting a microbial CH₄ supply from bottom sediment in the Yamato and Ulleung basins. We observed a local CH₄ plume over a deep channel east of the Yamato Basin, indicating unknown submarine CH₄ seepage with a microbial delta C-13 value of about -60 parts per thousand.

DOI： 10.1016/j.marchem.2011.10.006

琉球諸島周辺の地殻内部流体中のメタンの起源査読有り

土岐知弘，本田龍太郎，大嶺一希，岩田大吾，角皆潤，小松大祐，佐野有司，高畑直人，石橋純一郎，木下正高，山城秀之

地球化学 46 巻 ( 4 ) 頁： 257-274 2012年

Methane production and accumulation in the Nankai accretionary prism: Results from IODP Expeditions 315 and 316 査読有り

Geochemical Journal 46 巻 ( 2 ) 頁： 89-106 2012年

Variation in stable carbon and oxygen isotopes of individual benthic foraminifera: tracers for quantifying the magnitude of isotopic disequilibrium 査読有り

Ishimura, T., Tsunogai, U., Hasegawa, S., Nakagawa, F., Oi, T., Kitazato, H., Suga, H., Toyofuku, T.

Biogeosciences 9 巻頁： 4353-4367 2012年

Stable hydrogen isotopic analysis of nanomolar molecular hydrogen by automatic multi-step gas chromatographic separation 査読有り

Komatsu, Daisuke D., Tsunogai, Urumu, Kamimura, Kanae, Konno, Uta, Ishimura, Toyoho, Nakagawa, Fumiko

RAPID COMMUNICATIONS IN MASS SPECTROMETRY 25 巻 ( 21 ) 頁： 3351-3359 2011年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

We have developed a new automated analytical system that employs a continuous flow isotope ratio mass spectrometer to determine the stable hydrogen isotopic composition (delta D) of nanomolar quantities of molecular hydrogen (H₂) in an air sample. This method improves previous methods to attain simpler and lower-cost analyses, especially by avoiding the use of expensive or special devices, such as a Toepler pump, a cryogenic refrigerator, and a special evacuation system to keep the temperature of a coolant under reduced pressure. Instead, the system allows H₂ purification from the air matrix via automatic multi-step gas chromatographic separation using the coolants of both liquid nitrogen (77 K) and liquid nitrogen + ethanol (158 K) under 1 atm pressure. The analytical precision of the delta D determination using the developed method was better than 4 parts per thousand for >5 nmol injections (250 mL STP for 500 ppbv air sample) and better than 15 parts per thousand for 1 nmol injections, regardless of the delta D value, within 1 h for one sample analysis. Using the developed system, the delta D values of H₂ can be quantified for atmospheric samples as well as samples of representative sources and sinks including those containing small quantities of H₂, such as H₂ in soil pores or aqueous environments, for which there is currently little delta D data available. As an example of such trace H₂ analyses, we report here the isotope fractionations during H₂ uptake by soils in a static chamber. The delta D values of H₂ in these H₂-depleted environments can be useful in constraining the budgets of atmospheric H₂ by applying an isotope mass balance model.

DOI： 10.1002/rcm.5231

Nitrogen isotopes of organic nitrogen in reef coral skeletons as a proxy of tropical nutrient dynamics 査読有り

Yamazaki, Atsuko, Watanabe, Tsuyoshi, Tsunogai, Urumu

GEOPHYSICAL RESEARCH LETTERS 38 巻 2011年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

Understanding tropical nutrient dynamics is essential for quantifying marine productivity. In tropical and subtropical oceans, however, the spatial and continuous observation of nutrients has been scarce because of low nutrient concentration. The nitrogen isotopes of organic nitrogen in coral skeletons (delta¹⁵Ncoral) could be used to record nitrogenous nutrient origins at oceanic surfaces. Here, we show the intra- and inter-reef variations of delta¹⁵Ncoral in the western Pacific. The zonal distribution of delta¹⁵Ncoral was found inside a coral reef corresponding with delta¹⁵N of seawater nitrate (δ¹⁵N(nitrate)). The extended analysis of delta¹⁵Ncoral among various coral reefs also shows a latitudinal gradient from tropical to temperate in the western Pacific. The delta¹⁵Ncoral records high-resolution dynamics of nitrogenous nutrients through the geologic time scale.

DOI： 10.1029/2011GL049053

Hydrogen isotopes in volcanic plumes: Tracers for remote temperature sensing of fumaroles 査読有り

Tsunogai, U., K. Kamimura, S. Anzai, F. Nakagawa, D.D. Komatsu

GEOCHIMICA ET COSMOCHIMICA ACTA 75 巻 ( 16 ) 頁： 4531-4546 2011年8月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

In high-temperature volcanic fumaroles (>400 degrees C), the isotopic composition of molecular hydrogen (H₂) reaches equilibrium with that of the fumarolic H₂O. In this study, we used this hydrogen isotope exchange equilibrium of fumarolic H₂ as a tracer for the remote temperature at volcanic fumaroles. In this remote sensing, we deduced the hydrogen isotopic composition (delta D value) of fumarolic H₂ from those in the volcanic plume. To ascertain that we can estimate the delta D value of fumarolic H₂ from those in a volcanic plume, we estimated the values in three fumaroles with outlet temperatures of 630 degrees C (Tarumae), 203 degrees C (Kuju), and 107 degrees C (E-san). For this we measured the concentration and delta D value of H₂ in each volcanic plume, along with those determined directly at each fumarole. The average and maximum mixing ratios of fumarolic H₂ within a plume's total H₂ were 97 % and 99 % (at Tarumae), 89 % and 96 % (at Kuju), and 97 % and 99 % (at E-san). We found a linear relationship between the depletion in the delta D values of H₂, with the reciprocal of H₂ concentration. Furthermore, the estimated end-member delta D value for each H₂-enriched component (260 +/- 30 parts per thousand vs. VSMOW in Tarumae, 509 +/- 23 parts per thousand in Kuju, and 437 +/- 14 parts per thousand in E-san) coincided well with those observed at each fumarole (-247.0 +/- 0.6 parts per thousand in Tarumae, -527.7 +/- 10.1 parts per thousand in Kuju, and -432.1 +/- 2.5 parts per thousand in E-san). Moreover, the calculated isotopic temperatures at the fumaroles agreed to within 20 degrees C with the observed outlet temperature at Tarumae and Kuju. We deduced that the dD value of the fumarolic H2 was quenched within the volcanic plume. This enabled us to remotely estimate these in the fumarole, and thus the outlet temperature of fumaroles, at least for those having the outlet temperatures more than 400 degrees C. By applying this methodology to the volcanic plume emitted from the Crater 1 of Mt. Naka-dake (the volcano Aso) where direct measurement on fumaroles was impractical, we estimated that the dD value of the fumarolic H2 to be -172 +/- 16 parts per thousand and the outlet temperature to be 868 +/- 97 degrees C. The remote temperature sensing using hydrogen isotopes developed in this study is widely applicable to many volcanic systems.

DOI： 10.1016/j.gca.2011.05.023

A geochemical study on mud volcanoes in the Junggar Basin, China 査読有り

Nakada, Ryoichi, Takahashi, Yoshio, Tsunogai, Urumu, Zheng, Guodong, Shimizu, Hiroshi, Hattori, Keiko H.

APPLIED GEOCHEMISTRY 26 巻 ( 7 ) 頁： 1065-1076 2011年7月

記述言語：英語掲載種別：研究論文（学術雑誌）

A comprehensive study was performed to characterize, for the first time, the mud, water, and gases released from onshore mud volcanoes located in the southern margin of the Junggar Basin, northwestern China. Chemical compositions of mud, along with the geology of the basin, suggest that a source of the mud is Mesozoic or Cenozoic shale. Oxygen and H isotope compositions of the released water suggest a local meteoric origin. Combined with the positive Eu anomalies of the water, a large (18)O shift of the water suggests extensive interaction with rocks. Gases discharged from the mud volcanoes are predominantly thermogenic hydrocarbons, and the high delta¹³C values (>+20 parts per thousand VPDB) for CO₂ gases and dissolved carbonate in muddy water suggest secondary methanogenesis with CO₂ reduction after oil biodegradation. The enrichments of Eu and (18)O in water and the low thermal gradient of the area suggest that the water-rock interactions possibly occur deeper than 3670 +/- 200 m. On the other hand, considering the relationship to the petroleum reservoir around the mud volcanoes, the depth of the gases can be derived from about 3600 m, a depth that is greater than that generally estimated for reservoirs whose gas is characterized by ¹³C-enriched CO₂. Oil biodegradation with CO₂ reduction likely occurs at a shallower depth along the seepage system of the mud volcano. The results contribute to the worldwide data set of gas genesis in mud volcanoes. Moreover, they further support the concept that most terrestrial mud volcanoes release thermogenic gas produced in very deep sediments and may be early indicators of oil biodegradation, an important problem in the petroleum industry.

DOI： 10.1016/j.apgeochem.2011.03.011

Geophysical and geochemical evidence of large scale fluid flow within shallow sediments in the eastern Gulf of Mexico, offshore Louisiana 査読有り

Gay, A., Takano, Y., Gilhooly, III, W. P., Berndt, C., Heeschen, K., Suzuki, N., Saegusa, S., Nakagawa, F., Tsunogai, U., Jiang, S. Y., Lopez, M.

GEOFLUIDS 11 巻 ( 1 ) 頁： 34-47 2011年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

We analyse the fluid flow regime within sediments on the Eastern levee of the modern Mississippi Canyon using 3D seismic data and downhole logging data acquired at Sites U1322 and U1324 during the 2005 Integrated Ocean Drilling Program (IODP) Expedition 308 in the Gulf of Mexico. Sulphate and methane concentrations in pore water show that sulphate-methane transition zone, at 74 and 94 m below seafloor, are amongst the deepest ever found in a sedimentary basin. This is in part due to a basinward fluid flow in a buried turbiditic channel (Blue Unit, 1000 mbsf), which separates sedimentary compartments located below and above this unit, preventing normal upward methane flux to the seafloor. Overpressure in the lower compartment leads to episodic and focused fluid migration through deep conduits that bypass the upper compartment, forming mud volcanoes at the seabed. This may also favour seawater circulation and we interpret the deep sulphate-methane transition zones as a result of high downward sulphate fluxes coming from seawater that are about 5-10 times above those measured in other basins. The results show that geochemical reactions within shallow sediments are dominated by seawater downwelling in the Mars-Ursa basin, compared to other basins in which the upward fluid flux is controlling methane-related reactions. This has implications for the occurrence of gas hydrates in the subsurface and is evidence of the active connection between buried sediments and the water column.

DOI： 10.1111/j.1468-8123.2010.00304.x

Stable carbon isotope ratios of ethane over the North Pacific: Atmospheric measurements and global chemical transport modeling 査読有り

Saito, Takuya, Stein, Olaf, Tsunogai, Urumu, Kawamura, Kimitaka , Nakatsuka, Takeshi, Gamo, Toshitaka, Yoshida, Naohiro

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 116 巻 2011年1月

記述言語：英語掲載種別：研究論文（学術雑誌）

The atmospheric mixing ratios of ethane and its stable carbon isotope ratios (delta¹³C) were measured over the North Pacific (2 degrees N to 38 degrees N, 140 degrees E to 90 degrees W) during oceanographic cruises in summer and autumn. The measured mixing ratios were relatively low (mostly < 1 ppbv) over the North Pacific, whereas elevated ethane levels (> 1 ppbv) were observed over the western North Pacific near Japan, with lower delta¹³C values (approximately -25 parts per thousand), suggesting recent emissions from neighboring source regions. The most ¹³C-enriched values of ethane (approximately -16 parts per thousand) were observed over the western equatorial Pacific rather than the central and eastern equatorial Pacific. This is likely caused by the kinetic isotope effect (KIE) for the removal of ethane during the atmospheric transport from potential upwind source regions to the most remote region under the prevailing trade easterly winds. The measurements were compared with the results of a global chemical transport model including two ethane isotopologues ((12)C(2)H(6) and ¹³C(2)H(6)). The model-estimated delta¹³C values were too high compared with the observations. It is likely that this discrepancy is partly due to an approximately 40 % overestimation of the reported KIE for the reaction between ethane and OH radicals.

DOI： 10.1029/2010JD014602

Application of PTR-MS to an incubation experiment of the marine diatom Thalassiosira pseudonana 査読有り

Kameyama, Sohiko, Tanimoto, Hiroshi, Inomata, Satoshi, Suzuki, Koji, Komatsu, Daisuke D., Hirota, Akinari, Konno, Uta, Tsunogai, Urumu

GEOCHEMICAL JOURNAL 45 巻 ( 5 ) 頁： 355-363 2011年

記述言語：英語掲載種別：研究論文（学術雑誌）

Emission of trace gases from the marine diatom Thalassiosira pseudonana (CCMP 1335) was continuously monitored with a proton transfer reaction-mass spectrometry (PTR-MS) in an axenic batch culture system under a 13:11-h light:dark cycle. Substantial increases in the signals at m/z 49, 63, and 69, attributable to methanethiol, dimethyl sulfide (DMS), and isoprene, respectively, were observed in response to increases in cell density. Signals at m/z 69 showed diurnal variations throughout the experiment whereas those at m/z 49 were more pronounced at the beginning of the incubation. Interestingly, the signals at m/z 49 and 69 changed immediately following the light-dark and dark-light transitions, suggesting that light plays a crucial role in the production of methanethiol and isoprene. However, in the latter half of the experiment, methanethiol showed negligible diurnal variations regardless of light conditions, suggesting the production of methanethiol from enzymatic cleavage of DMS. The trend ill signals at m/z 63 was similar to that of the abundance of senescent cells plus cell debris rather than vegetative cells. The results suggest that aging or death of phytoplankton cells could also substantially control DMS production in natural waters along with the other microbial processes related to bacteria and zooplankton.

Quantifying nitrate dynamics in an oligotrophic lake using Δ¹⁷O 査読有り

Tsunogai, U., Daita, S., Komatsu, D. D., Nakagawa, F., Tanaka, A.

BIOGEOSCIENCES 8 巻 ( 3 ) 頁： 687-702 2011年

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

The stable isotopic compositions of nitrate, including the ¹⁷O anomalies (Delta¹⁷O), were determined twice in 1 yr (June and August 2007) in the oligotrophic water column of Lake Mashu, Japan. These data were then used to quantify the geochemical dynamics of nitrate in the lake, by using the deposition rate of the atmospheric nitrate onto the entire catchment area of the lake. The total amount of nitrate in the lake water decreased from 4.2 to 2.1 Mmol during the period between the observations, while the average Delta¹⁷O values remained uniform at + 2.5 parts per thousand. The Delta¹⁷O values corresponded to an small and uniform mixing ratio of atmospheric nitrate to total nitrate of 9.7 +/- 0.8 %. These results indicate that 0.52 +/- 0.34 Mmol of the remineralized nitrate was fed into the water column through nitrification, while 2.6 +/- 0.4 Mmol of nitrate was simultaneously removed from the water column by assimilation, during the period between the observations. The lake water dissolved nitrate was characterized by rapid removal through assimilation during summer until it was almost completely removed from the euphotic layer, as well as continuous feeding into the lake through nitrification (3.2 +/- 0.3 Mmol a(-1)) and deposition (0.35 +/- 0.2 Mmol a(-1)), regardless of the seasons. The ¹⁵N-depleted nitrogen isotopic compositions of nitrate were as low as -6.5 parts per thousand in June, which also indicates that in-lake nitrification is the major source of nitrate in the lake and suggests that there is low potential for denitrification in and around the lake. Atmospheric nitrate deposited into the lake will be assimilated quickly, having a mean residence time of 1.2 +/- 0.1 yr. In addition, more than 90 % of the assimilated nitrate will be remineralized to nitrate and re-assimilated via active nitrogen cycling in the lake.

DOI： 10.5194/bg-8-687-2011

Diversity and Function of Epibiotic Microbial Communities on the Galatheid Crab, Shinkaia crosnieri 査読有り

Watsuji, Tomo-o, Nakagawa, Satoshi, Tsuchida, Shinji, Toki, Tomohiro, Hirota, Akinari, Tsunogai, Urumu, Takai, Ken

MICROBES AND ENVIRONMENTS 25 巻 ( 4 ) 頁： 288-294 2010年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

The galatheid crab, Shinkaia crosnieri (Decapoda: Galatheidae), forms dense colonies in the Iheya North and Hatoma Knoll deep-sea hydrothermal fields and has numerous setae covered with filamentous epibiotic microorganisms. Molecular phylogenetic analyses revealed that the epibiotic communities in S. crosnieri consisted mainly of yet-uncultivated phylotypes within Epsilonproteobacteria and Gammaproteobacteria in both hydrothermal vent fields. Uptake experiments using ¹³C-labeled tracers clearly demonstrated that both H¹³CO(3)(-) and ¹³CH₄ were assimilated into not only the epibiotic microbial communities associated with the setae, but also the epibiont-free tissue of living S. crosnieri. In addition, the incorporation of H¹³CO(3)(-) into the microbial cells was strongly stimulated by the presence of reduced sulfur compounds but not by H₂. In conclusion, the uptake experiments suggested that sulfur-oxidizing chemolithoautotrophic and methanotrophic production by the epibionts provides the nutrition for S. crosnieri.

DOI： 10.1264/jsme2.ME10135

High-resolution measurement of multiple volatile organic compounds dissolved in seawater using equilibrator inlet-proton transfer reaction-mass spectrometry (EI-PTR-MS) 査読有り

Kameyama, Sohiko, Tanimoto, Hiroshi, Inomata, Satoshi, Tsunogai, Urumu, Ooki, Atsushi, Takeda, Shigenobu, Obata, Hajime, Tsuda, Atsushi, Uematsu, Mitsuo

MARINE CHEMISTRY 122 巻 ( 40912 ) 頁： 59-73 2010年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

We developed an equilibrator inlet-proton transfer reaction-mass spectrometry (EI-PTR-MS) system for high-resolution measurement of the concentrations of multiple volatile organic compounds (VOCs) dissolved in seawater. The equilibration of five VOCs (isoprene, propene, acetone, acetaldehyde, and methanol) between seawater samples and the carrier gas, and the response time of the system, were evaluated by means of a series of laboratory experiments. Although equilibrium between the seawater sample and the carrier gas in the equilibrator was not achieved for isoprene and propene (likely because of their low water solubility), the other species did reach equilibrium. The EI-PTR-MS system was deployed during a research cruise in the western North Pacific Ocean. Evaluation of several seawater sampling methods indicated that there was no significant contamination from the sampling apparatus for the target VOCs. For isoprene, comparison of EI-PTR-MS measurements with measurements obtained with a membrane equilibrator-gas chromatography/mass spectrometry system showed generally good agreement (R(2)=0.79). EI-PTR-MS captured the temporal variations of dissolved VOCs, including small-scale variability, which demonstrates that the performance of the EI-PTR-MS system was sufficient for simultaneous and continuous measurements of multiple VOCs of environmental importance in seawater.

DOI： 10.1016/j.marchem.2010.08.003

Geomicrobiological Properties of Ultra-Deep Granitic Groundwater from the Mizunami Underground Research Laboratory (MIU), Central Japan 査読有り

Fukuda, Akari, Hagiwara, Hiroki, Ishimura, Toyoho, Kouduka, Mariko, Ioka, Seiichiro, Amano, Yuki, Tsunogai, Urumu, Suzuki, Yohey, Mizuno, Takashi

MICROBIAL ECOLOGY 60 巻 ( 1 ) 頁： 214-225 2010年7月

記述言語：英語掲載種別：研究論文（学術雑誌）

Although deep subterranean crystalline rocks are known to harbor microbial ecosystems, geochemical factors that constrain the biomass, diversity, and metabolic activities of microorganisms remain to be clearly defined. To better understand the geochemical and microbiological relationships, we characterized granitic groundwater collected from a 1,148- to 1,169-m-deep borehole interval at the Mizunami Underground Research Laboratory site, Japan, in 2005 and 2008. Geochemical analyses of the groundwater samples indicated that major electron acceptors, such as NO (3) (-) and SO (4) (2-) , were not abundant, while dissolved organic carbon (not including organic acids), CH₄ and H₂, was moderately rich in the groundwater sample collected in 2008. The total number of acridine orange-stained cells in groundwater samples collected in 2005 and 2008 were 1.1 x 10(4) and 5.2 x 10(4) cells/mL, respectively. In 2005 and 2008, the most common phylotypes determined by 16S rRNA gene sequence analysis were both related to Thauera spp., the cultivated members of which can utilize minor electron donors, such as aromatic and aliphatic hydrocarbons. After a 3-5-week incubation period with potential electron donors (organic acids or CH₄ + H₂) and with/without electron acceptors (O(2) or NO (3) (-) ), dominant microbial populations shifted to Brevundimonas spp. These geomicrobiological results suggest that deep granitic groundwater has been stably colonized by Thauera spp. probably owing to the limitation of O(2), NO (3) (-) , and organic acids.

DOI： 10.1007/s00248-010-9683-9

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